Introduction of mass spectrometry as a label free detection technique for HTS has been explore during the past several years. Main limitations are the throughput and the volume of sample required. The Luxon ion source based on Laser Diode Thermal Desorption (LDTD) enables analysis time of 0.91 seconds when coupled to mass spectrometry. Assays with amino acid marker pose a difficulty to thermal desorption technique as their volatility is limited. Enhancement of vaporization by derivatization was employed for analyzing of amino acid in GC-MS system in early 70s. Several of those reagents are tested and optimized to achieve the analysis of amino acid in accordance with the complete workflow throughput required. It operates with samples of 1 µL deposited onto a 384-LazWell plate followed by the addition of 500 nL of reagent using the Gyger Certus non-contact liquid disperser in 13 seconds. Reaction occurs during sample drying step within 2 minutes for a complete evaporation of solvent. Tryptophan, Kynurenine, N-Formyl Kynurenine and 3-OH-Kynurenine are quantified using MRM transition of FMOC derivative. Molecules produced are stable in dry state with sufficient volatility and good ionization capability. Good accuracy (88.7 to 103.5 %) and precision (3.7 to 9.7 %) are obtained and excellent linearity (R2= 0.99721 to 0.99910) is achieved for Tryptophan, Kynurenine and N-Formyl Kynurenine. 3-OH-Kynurenine measurement needs more investigation. Derivatization includes molecular rearrangement to the addition of FMOC. Using of marked compound with 2C13, N15 was necessary to identify the according structure. Quantitation is obtained using IS ratio from 20 to 10000 ng/ml. Accuracy (85.6 to 114.3 %) and precision (2.7 to 13.7 %) are obtained and linearity (R2= 0.9981) is achieved. Luxon ion source give label free detection at similar speed per sample than a plate reader with the benefit of the mass spectrometry detection and this with small sample size.

Primary Author - February Poster(s)

Pierre Picard

Vice-president RandDPhytronix TechnologiesQuebec, Quebec, Canada

Ph. D. in Physic (Université Laval, Québec, Canada) on vacuum free jet expansion and ion optics
Co-founder of Phytronix Technologies in 2000
Inventor of LDTD ion source in 2005
Development of the Luxon Ion source, second generation of LDTD in 2016
Researcher on fundamental and applications of LDTD technology